Make [TreatNullAs=NullString] DOMString arguments nullable instead

Source/core/dom/Element.idl

 /*
  * Copyright (C) 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 21 matching lines @@
     [MeasureAs=ElementGetAttributeNode] Attr getAttributeNode([Default=Undefined] optional DOMString name); // Removed from DOM4.
     [RaisesException, CustomElementCallbacks, MeasureAs=ElementSetAttributeNode] Attr setAttributeNode([Default=Undefined] optional Attr newAttr); // Removed from DOM4.
     [RaisesException, CustomElementCallbacks, MeasureAs=ElementRemoveAttributeNode] Attr removeAttributeNode([Default=Undefined] optional Attr oldAttr); // Removed from DOM4.
     HTMLCollection getElementsByTagName(DOMString name);
 
     [PerWorldBindings, ImplementedAs=attributesForBindings] readonly attribute NamedNodeMap     attributes;
     [MeasureAs=HasAttributes] boolean hasAttributes();
 
     // DOM Level 2 Core
 
-    DOMString? getAttributeNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);
-    [RaisesException, CustomElementCallbacks] void setAttributeNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString qualifiedName, DOMString value);
-    [CustomElementCallbacks] void removeAttributeNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);
-    HTMLCollection getElementsByTagNameNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);
-    [MeasureAs=ElementGetAttributeNodeNS] Attr getAttributeNodeNS([TreatNullAs=NullString, Default=Undefined] optional DOMString namespaceURI,
+    DOMString? getAttributeNS(DOMString? namespaceURI, DOMString localName);
+    [RaisesException, CustomElementCallbacks] void setAttributeNS(DOMString? namespaceURI, DOMString qualifiedName, DOMString value);
+    [CustomElementCallbacks] void removeAttributeNS(DOMString? namespaceURI, DOMString localName);
+    HTMLCollection getElementsByTagNameNS(DOMString? namespaceURI, DOMString localName);
+    [MeasureAs=ElementGetAttributeNodeNS] Attr getAttributeNodeNS([Default=Undefined] optional DOMString? namespaceURI,
                                                                   [Default=Undefined] optional DOMString localName); // Removed from DOM4.
     [RaisesException, CustomElementCallbacks, DeprecateAs=ElementSetAttributeNodeNS] Attr setAttributeNodeNS([Default=Undefined] optional Attr newAttr); // Removed from DOM4.
     boolean hasAttribute(DOMString name);
-    boolean hasAttributeNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);
+    boolean hasAttributeNS(DOMString? namespaceURI, DOMString localName);
 
     [PerWorldBindings] readonly attribute CSSStyleDeclaration style;
 
     // DOM4
     [Reflect] attribute DOMString id;
     readonly attribute DOMString? namespaceURI;
     [RaisesException=Setter] attribute DOMString? prefix;
     readonly attribute DOMString? localName;
 
     [RaisesException] boolean matches(DOMString selectors);
@@ skipping 78 matching lines @@
     [RuntimeEnabled=Touch] attribute EventHandler ontouchend;
     [RuntimeEnabled=Touch] attribute EventHandler ontouchmove;
     [RuntimeEnabled=Touch] attribute EventHandler ontouchstart;
     attribute EventHandler onwebkitfullscreenchange;
     attribute EventHandler onwebkitfullscreenerror;
     attribute EventHandler onwheel;
 };
 
 Element implements ParentNode;
 Element implements ChildNode;